First report of molecular confirmation and phylogenetic analysis of ocular seteriasis in buffalo in India using 12S rRNA

An adult Indian buffalo (Bubalus bubalis) presented with corneal opacity, irritation, and excessive lacrimation from the left eye in the Referral Veterinary Polyclinic-Teaching Veterinary Clinical Complex (RVC-TVCC), Indian Veterinary Research Institute, Izatnagar. Clinical examination revealed a whitish thread-like worm in the left eye's anterior chamber. The worm was surgically removed from the eye with supportive nerve blocks. Light microscopy was used for parasite morphological identification, which provided insight into the worm as female Setaria sp. Genomic DNA was isolated, and polymerase chain reaction amplification of 12S rRNA was conducted for molecular confirmation of the parasite. The amplicon was sequenced and analysed by bioinformatics software. Sequence data showed an amplicon size of 243 bp. Phylogenetic analysis with reference data from the NCBI Genbank database revealed the worm was S. digitata, with a similarity of 99.17%. The common predilection site of S. digitata is in the peritoneal cavity of natural hosts like cattle and buffalo and is mostly non-pathogenic. The aberrant migration of the parasite larva to the brain and eye commonly occurs in goats, sheep, and horses, causing clinical conditions like cerebrospinal nematodiasis (lumbar paralysis) and ocular setariasis, respectively. Nevertheless, until now, there have been no reports of ocular setariasis in buffalo. This report is the first unusual occurrence of ocular setariasis in buffalo and its molecular confirmation and phylogenetic analysis using 12S rRNA.

First Report of Rubber Collection Bowls & Plastic and Bamboo Water Containers as the Major Breeding Source of Ae. albopictus with the Indigenous Transmission of Dengue and Chikungunya in Rural Forested Malaria-Endemic Villages of Dhalai District, Tripura, India: The Importance of Molecular Identification

BACKGROUND

With the reports of indigenous cases of dengue and chikungunya in the forest-covered rural tribal malaria-endemic villages of Dhalai District, Tripura, India, an exploratory study was undertaken to identify the vector breeding sites.

METHODS

From June 2021 to August 2022, mosquito larvae were collected from both natural and artificial sources in the villages, house premises, and their nearby forested areas outside of the houses. Other than morphological characterisation, Aedes species were confirmed by polymerase chain reaction targeting both nuclear (ITS2) and mitochondrial genes (COI) followed by bidirectional Sanger sequencing.

RESULTS

Aedes albopictus was abundantly found in this area in both natural and artificial containers, whereas Ae. aegypti was absent. Among the breeding sources of molecularly confirmed Ae. albopictus species, rubber collection bowls were found to be a breeding source reported for the first time. Plastic and indigenously made bamboo-polythene containers for storing supply water and harvesting rainwater in the villages with a shortage of water were found to be other major breeding sources, which calls for specific vector control strategies. Natural sources like ponds and rainwater collected on Tectona grandis leaves and Colocasia axil were also found to harbour the breeding, along with other commonly found sources like bamboo stumps and tree holes. No artificial containers as a breeding source were found inside the houses. Mixed breeding was observed in many containers with other Aedes and other mosquito species, necessitating molecular identification. We report six haplotypes in this study, among which two are reported for the first time. However, Aedes aegypti was not found in the area. Additionally, rubber collection bowls, ponds, and water containers also showed the presence of Culex quinquefasciatus and Culex vishnui, known JE vectors from this area, and reported JE cases as well. Different Anopheles vector spp. from this known malaria-endemic area were also found, corroborating this area as a hotbed of several vectors and vector-borne diseases.

CONCLUSIONS

This study, for the first time, reports the breeding sources of Aedes albopictus in the forested areas of Tripura, with rubber collection bowls and large water storage containers as major sources. Also, for the first time, this study reports the molecular characterisation of the Ae. albopictus species of Tripura, elucidating the limitations of morphological identification and highlighting the importance of molecular studies for designing appropriate vector control strategies. The study also reports the co-breeding of JE and malaria vectors for the first time in the area reporting these vector-borne diseases.

A Multiplex PCR Based on Mitochondrial COI Sequences for Identification of Members of the Anopheles barbirostris Complex (Diptera: Culicidae) in Thailand and Other Countries in the Region

A multiplex-PCR assay based on mitochondrial cytochrome c oxidase subunit I (COI) sequences was developed for identification of five members of the Barbirostris Complex which occur in Thailand: Anopheles barbirostris s.s., An. dissidens, An. saeungae, An. wejchoochotei and An. barbirostris species A3. Anopheles campestris was not included in the assay due to the lack of unequivocal sequences. Allele-specific primers were designed for specific nucleotide segments of COI sequences of each species. Mismatch method and addition of long GC tail were applied for some primers. The assay provided products of 706 bp for An. barbirostris s.s., 238 bp for An. dissidens, 611 bp for An. saeungae, 502 bp for An. wejchoochotei and 365 bp for An. barbirostris A3. The assay was tested using 111 wild-caught female mosquitoes from Bhutan, Cambodia, Indonesia (Sulawesi) and Thailand. The results of the multiplex PCR were in complete agreement with COI sequencing; however, one of three specimens from Bhutan and all 11 specimens from Indonesia were not amplifiable by the assay due to their distinct COI sequences. This, together with the distinct rDNA sequences of these specimens, suggests the presence of at least two additional new species in the Barbirostris Complex.

Systematic studies of Anopheles (Cellia) kochi (Diptera: Culicidae): Morphology, cytogenetics, cross-mating experiments, molecular evidence and susceptibility level to infection with nocturnally subperiodic Brugia malayi

Anopheles kochi Dӧnitz (Diptera: Culicidae) is a malaria vector in some countries in South and Southeast Asia. This is the first report to provide clear evidence that two different cytological forms of An. kochi are conspecific based on systematic studies. Two karyotypic forms, i.e., Form A (X₁, X₂, Y₁) and a novel Form B (X₁, X₂, Y₂) were obtained from a total of 15 iso-female lines collected from five provinces in Thailand. Form A was common in all provinces, whereas Form B was restricted to Ubon Ratchathani province. This study determined whether the two karyotypic variants of An. kochi exist as a single or cryptic species by performing cross-mating experiments in association with the sequencing of the second internal transcribed spacer (ITS2) of ribosomal DNA (rDNA), and cytochrome c oxidase subunit I (COI) of mitochondrial DNA (mtDNA). Cross-mating experiments between the two karyotypic forms revealed genetic compatibility by providing viable progenies through F₂ generations. The two forms showed a high sequence similarity of those two DNA regions (average genetic distances: ITS2 = 0.002-0.005, COI = 0.000-0.009). The phylogenetic trees based on ITS2 and COI sequences also supported that four strains (from Bhutan, Cambodia, Indonesia, and Thailand) were all of the same species. Five sensilla types housed on the antennae of female An. kochi were observed under scanning electron microscopy (SEM). In addition, this study found that An. kochi was a refractory vector, revealed by 0% susceptibility rates to infection with nocturnally subperiodic Brugia malayi. The cibarial armature was a resistant mechanism, as it killed the microfilariae in the foregut before they penetrated into the developmental site.

Description of Aedes (Hulecoeteomyia) bhutanensis n. sp. (Diptera: Culicidae) from Bhutan

A new species of the subgenus Hulecoeteomyia of the genus Aedes reared from pupae found with two larvae in a small pool on a log in mountainous forest of Bhutan is diagnosed and formally named Aedes bhutanensis Somboon & Harbach, n. sp. The specific status of the species is supported by differential morphological characters of females, larvae and pupae, and sequences of the mitochondrial COI gene. Dichotomous keys are provided for identification of the adult females and larvae of the species of the subgenus.

Malaria in North-East India: Importance and Implications in the Era of Elimination

Worldwide and in India, malaria elimination efforts are being ramped up to eradicate the disease by 2030. Malaria elimination efforts in North-East (NE) India will have a great bearing on the overall efforts to eradicate malaria in the rest of India. The first cases of chloroquine and sulfadoxine-pyrimethamine resistance were reported in NE India, and the source of these drug resistant parasites are most likely from South East Asia (SEA). NE India is the only land route through which the parasites from SEA can enter the Indian mainland. India’s malaria drug policy had to be constantly updated due to the emergence of drug resistant parasites in NE India. Malaria is highly endemic in many parts of NE India, and Plasmodium falciparum is responsible for the majority of the cases. Highly efficient primary vectors and emerging secondary vectors complicate malaria elimination efforts in NE India. Many of the high transmission zones in NE India are tribal belts, and are difficult to access. The review details the malaria epidemiology in seven NE Indian states from 2008 to 2018. In addition, the origin and evolution of resistance to major anti-malarials are discussed. Furthermore, the bionomics of primary vectors and emergence of secondary malaria vectors, and possible strategies to prevent and control malaria in NE are outlined.

A checklist of the Anopheles mosquito species (Diptera: Culicidae) in Bhutan

The present paper records, for the first time, the Anopheles fauna of Bhutan, determined from surveys conducted from 2007 to early 2018. Adult mosquitoes were collected mainly on cattle bait and occasionally in human landing catches. Collections of immature stages were performed in various aquatic habitats. Larvae were preserved or reared to adults. Identification was based on morphological characters using available keys. A total of 30 species were identified, including nine species of subgenus Anopheles and 21 species of subgenus Cellia. Distribution and collection data are provided with notes on the locations and habitats of the species. Anopheles pseudowillmori is suspected to be a vector of malarial parasites in the plains and hilly forested areas of the country because it is widely distributed and the most common species collected in human landing catches. Notes also include observed morphological variation observed in An. baileyi and An. lindesayi, which differ from the type forms. Corrections are made for previous reports of Anopheles in Bhutan. The need for further surveys and molecular identification of members of species complexes and morphological variants is emphasized.

DNA barcoding of five Japanese encephalitis mosquito vectors (Culex fuscocephala, Culex gelidus, Culex tritaeniorhynchus, Culex pseudovishnui and Culex vishnui)

Culex mosquitoes can act as vectors of several important diseases, including Japanese encephalitis, West Nile virus, St. Louis encephalitis and equine encephalitis. Besides the neurological sequelae caused in humans, Japanese encephalitis can lead to abortion in sows and encephalitis in horses. Effective vector control and early diagnosis, along with continuous serosurveillance in animals, are crucial to fight this arboviral disease. However, the success of vector control operations is linked with the fast and reliable identification of targeted species, and knowledge about their biology and ecology. Since the DNA barcoding of Culex vectors of Japanese encephalitis is scarcely explored, here we evaluated the efficacy of this tool to identify and analyze the variations among five overlooked Culex vectors of Japanese encephalitis, Culex fuscocephala, Culex gelidus, Culex tritaeniorhynchus, Culex pseudovishnui and Culex vishnui, relying to the analysis of mitochondrial CO1 gene. Variations in their base pair range were elucidated by the entropy H_x plot. The differences among individual conspecifics and on base pair range across the same were studied. The C (501-750 bp) region showed a moderate variation among all the selected species. C. tritaeniorhynchus exhibited the highest variation in all the ranges. The observed genetic divergence was partially non-discriminatory. i.e., the overall intra- and inter nucleotide divergence was 0.0920 (0.92%) and 0.125 (1.25%), respectively. However, 10X rule fits accurately intraspecies divergence <3% for the five selected Culex species. The analysis of individual scatter plots showed threshold values (10X) of 0.008 (0.08%), 0.005 (0.05%), 0.123 (1.23%), 0.033 (0.33%) and 0.019 (0.19%) for C. fuscocephala, C. gelidus, C. tritaeniorhynchus, C. pseudovishnui and C. vishnui, respectively. The C. tritaeniorhynchus haplotypes KU497604, KU497603, AB690847 and AB690854 exhibited the highest divergence range, i.e., from 0.465 -0.546. Comparatively, the intra-divergence among the other haplotypes of C. tritaeniorhynchus ranged from 0-0.056. The maximum parsimony tree was formed by distinctive conspecific clusters with appreciable branch values illustrating their close congruence and extensive genetic deviations. Overall, this study adds valuable knowledge to the molecular biology and systematics of five overlooked mosquito species acting as major vectors of Japanese encephalitis in Asian countries.